WO 2009055997 describes a process for producing propylene from ethylene and methanol (or/and dimethyl ether), which is characterized in that the gas containing methanol (or/and dimethyl ether) and the gas containing ethylene are contacted together with a catalyst which has a pore diameter of 0.3 nm-0.5 nm and a saturated NH3 adsorption amount of 0.8 mmol/g-2.5 mmol/g at 200° C., to obtain the products containing propylene. The reaction conditions are as follows: the molar ratio of ethylene/methanol (or 2 times dimethyl ether) is 0.1-2, the reaction temperature is 300-600° C., preferably 350° C.-550° C. and the reaction pressure is 0.01-0.8 MPa. The propylene yield of products may be more than 60 C % based on the methanol. In the examples the catalyst is a SAPO 34 and the reaction temperature is 400° C. This reaction is not selective, it produces also C3-C6.
In “Co-reaction of ethene and methanol over modified H-ZSM-5” by Jinzhe Li et al published in Catalysis Communications 9 (2008) pages 2515-2519 is described the co reaction of ethylene and methanol over HZSM-5, P-La modified ZSM-5 (PLaHZ) and hydrothermal-treated PLaHZ catalysts. The reaction temperatures are from 450° C. to 550° C. At 500° C., methanol WHSV=3.5 h-1, ethene WHSV=5.7 h-1, time on stream (TOS)=6 min, the methanol conversion is 60.8%, the ethylene conversion is 11.3%, the production comprises 52.9% of propylene, 19.8% of butenes and 24% of C5+. With the same operating conditions at TOS=100 minutes the propylene % increases to about 70%.
In “Direct observation of olefin homologations on zeolite ZSM-22 and its implications to methanol to olefin conversion” by Zhi-Min Cui et al published in Journal of Catalysis 258 (2008) pages 83-86 is described olefin homologation (methylation of the olefin C═C double bond) on ZSM-22. Homologation of ethylene, propylene and styrene were directly observed between 13C labeled methanol and olefins. Isotopic tracking shows high selectivity for homologation reaction, e.g. from ethylene, propene has one 13C atom, butene has two 13C atoms, and pentene has three 13C atoms. The reaction temperatures are from 300° C. to 400° C., the production comprises about similar proportions of propylene, butene and pentene.
U.S. 2006-0229482 describes a process for producing propylene, comprising: contacting a reaction mixture of ethylene and methanol and/or dimethyl ether in the presence of a catalyst while controlling the amount of ethylene that is discharged from the reaction system to a reduced level in comparison to the amount of ethylene that is being fed into the reaction system, and while controlling the yield of propylene to at least 40 mol %, based on the sum of the number of moles of methanol and two times the number of moles of dimethyl ether, which are being fed into the reaction system. The reaction temperature employed depends on the type of the catalyst used, but is usually at least about 200° C., preferably at least about 250° C., more preferably at least about 300° C., and the upper limit is usually at most about 700° C., preferably at most about 600° C., more preferably at most about 500° C. The reaction Conditions are:                Reaction temperature: 400° C.        Methanol: 6.5 mol %        Ethylene/methanol (molar ratio)=5        Water/methanol (molar ratio)=4        Methanol WHSV=0.5 h−1         
The methanol conversion is 100%, the catalyst is ZSM-5 or SAPO-34 and the hydrocarbon composition in the discharged component from the reactor comprises 61 to 73% of ethylene, 14 to 28% of propylene and 3 to 10% of butene. All examples are made with CH3OH at 400° C. or above.
WO 2007 135053 describes a process for the preparation of C5 and/or C6 olefins from a lower olefin, which lower olefin comprises from 2 to 5 carbon atoms, and an oxygenate, which oxygenate comprises at least one oxygen-bonded alkyl group, comprising contacting the lower olefin with the oxygenate, in a molar ratio of oxygen-bonded alkyl group to lower olefin of at least 1:1 in the presence of a MTT-type zeolite. In example 1 and comparative example A 2-methyl-2-butene (2M2B) and dimethylether (DME) were reacted in a molar feed ratio 2M2B:DME of 2:1 over a MFI-type (comparative) and a MIT-type zeolite (according to the invention) at a temperature of 325° C. In example 2,2-methyl-2-butene (2M2B) and dimethylether (DME) were reacted in a molar feed ratio 2M2B:DME of 2:1 over a MTT-type zeolite at a temperature of 450° C.
It has now been discovered that propylene can be efficiently produced from DME or DME+MeOH and ethylene at temperature below 300° C. with selectivity higher than 60% on the base on converted carbon. Without being binded by any explanation it seems that the introduction of an ethylene containing feedstock in the DME feed changes the usual MTO reaction route to more kinetically quick homologation. Moreover, under these conditions the contribution of oligomerization/cracking reactions is relatively low and may be even more suppressed in the presence of steam at the inlet of reactor. This leads to very high propylene selectivity from ethylene and MeOH (the precursor of DME). The propylene selectivity on carbon basis is the wt ratio of carbon in propylene in the reactor effluent (outlet of the reactor) to the converted carbon in the reactor. The proposed solution allows producing propylene with a selectivity higher than 60% on carbon basis.